Servosystem for sewing machines



April 12, 1966 G. MYSKA 3,245,369

SERVOSYSTEM FOR SEWING MACHINES Filed Oct. 22, 1963 6 Sheets-Sheet 1 INVENTOR. GUN TER MYSKA AGENT A ril 12, 1966 G. MYSKA 3,245,369

SERVOSYS'I'EM FOR SEWING MACHINES Filed Oct. 22, 1963 6 Sheets-Sheet 2 INVENTOR. GUNTER MYSKA AGENT.

April 12, 1966 e. MYSKA SERVOSYSTEM FOR SEWING MACHINES 6 Sheets-Sheet 5 Filed Oct. 22, 1963 INVENTOR. GUNTER MYSKA AGENT April 12, 1966 G. MYSKA 3,245,369

SERVOSYSTEM FOR SEWING MACHINES Filed Oct. 22, 1963 6 Sheets-Shee1i 4 ji W5 m INVENTOR. GUN TER MYSKA BY I A KRnS w AGENT April 12, 1966 G. MYSKA SERVOSYSTEM FOR SEWING MACHINES 6 Sheets-Sheet 5 Filed Oct. 22, 1963 E mm mm V NR E m "U G April 12, 1966 G. MYSKA SERVOSYSTEM FOR SEWING MACHINES 6 Sheets-Sheet 6 Filed Oct. 22, 1963 MENU Illil'll Iiii PULSE SHARPE NE R AMPLIFIER INVENTOR. GUN TER MYSKA United States Patent G werke A.G., Bielefeld, Germany, a corporation of Germany Filed Oct. 22, 1963, Ser. No. 317,952 Claims priority, applicatign Germany, Oct. 24, 1962,

D 11 Claims. (Cl.112-67) My present invention relates to sewing machines and, more specifically, to machines of the group-stitch type, e.g. as disclosed in my prior US. Patents Nos. 2,906,217 and 3,025,444, in which a sewing cycle is performed in a predetermined manner with the aid of a timing device or programpnit adapted to repeat the same cycle over and over again.

Machines of this type are used for the stitching of buttons, buttonholes, hinges and so forth.

To initiate the sewing cycle of the machine, an operator may actuate a manual control lever (the term being intended to include foot-operated elements such as pedals) or a start signal may be produced by an automatic detector, such as a photoelectric scanner, responsive to the approach of a properly positioned workpiece. When this occurs, the presser foot of the machine is lowered onto the workpiece to clamp the latter against the worktable whereupon the feeding mechanism is set in motion, along with the needle drive, to start the stitching operation controlled by the program unit. The latter step is usually accomplished by actuating a clutch which couples a continuously running motor to a drive shaft.

The means heretofore used for the raising and lowering of the presser foot were usually electromagnetic devices such as solenoids which are characterized by a rapid action that is not always desirable in the clamping of sensitive fabrics or the like. It is, therefore, an object of this invention to provide a manually or automatically controlled servosystem for sewing machines, adapted to initiate a predetermined operating cycle in the general manner described above, which acts more gradually upon the work-clamping mechanism of the machine than do conventional electrical systems.

A more specific object of the invention is to utilize, for the operation of sewing machines in a commercial establishment, the power of a source of fluid pressure frequently available, e.g. in the form of steam supplied to clothes presses, in such establishments.

It is also an object of my invention to provide a servosystem which can be conveniently installed in existing machinery.

A further object of my invention is to provide an assembly for such servosystem which utilizes only a small number of basic parts so designed as to accommodate various types of pneumatic units.

The servosystem conforming to my present invention includes fiuid-pressure-responsive means, preferably of the pneumatic type, for successively operating the clamping assembly of a sewing machine and the starter for its Work-feed and sewing mechanism. More specifically, the system comprises a single control element so coupled with two pneumatic drives as to result in their successive operation in a predetermined order, with actuation of the clamping means by the first drive and of the start means for the sewing and feed mechanism by the second drive.

Such a system may also be used for the simultaneous control of more than one sewing machine, eg a pair of such machines operating simultaneously on a single fabric as described in my copending application Ser. No. 223,466, filed September 13, 1962.

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The invention will be .described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a perspective view of a support table for a sewing machine equipped with a pneumatic servosystem according to my invention;

FIG. 2 is a perspective bottom view of the table, showing additional elements of the system;

FIG. 3 is a perspective view, drawn to a larger scale, of a mounting plate forming part of the system of FIGS. 1 and 2;

FIG. 4 is a view similar to FIG. 3, showing components of the pneumatic system mounted on the plate;

FIG. 5 is a perspective view of a yoke member also supporting certain components of the system;

FIG. 6 similarly illustrates an identical yoke member supporting other components;

FIG. 7 is a sectional view on the line VI IVII of FIG. 6;

FIG. 8 is a perspective view showing a second mounting plate with additional components carried thereon;

FIG. 9 is a view similar to FIG. 4, illustrating a modified assembly carried on the first-mentioned mounting late; p FIG. 10 is a detail view (parts broken away) of the mechanism of FIG. 9;

FIG. 11 is a sectional view taken on line XI-XI of FIG. 10;

FIG. 12 is a view similar to FIG. 5, showing the yoke member thereof with a modified assembly of components;

FIG. 13 is a sectional view similar to FIG. 7 but taken on the line XIII-XIII of FIG. 12;

FIG. 14 is a diagrammatic view of the pneumatic system illustrated in FIGS. 1-8;

FIG. 15 is a diagram similar to that of FIG. 14 but relating to a system incorporating an assembly of the type shown in FIG. 9;

FIG. 16 is a further diagram for a system comprising the assembly of FIG. 12; and

FIG. 17 is a diagram directed to still another modification.

In FIGS. 1 and 2 I have shown a table 59 which supports a sewing machine 80, the latter being provided with the usual mechanism for operating on a fabric or other workpiece as the latter is clamped between a base 86 and a presser foot 87 which may be manually controlled by means of a lever 31. The clamping mechanism, represented by lever 31 and foot 87, is also linked to a control rod 46 extending downwardly through the table 59, a similar control rod 46' being linked to the starting handle (not shown) for setting the sewing and feed mechanism in motion by coupling it to an electromotor 65 which is kept continuously running during and between operating cycles. The starting and stopping of motor 65 can be controlled by an on-ofI switch 64 whose handle 63 projects upwardly through a slot in table 59.

A pedal 68, disposed between the legs 69 of the table, is articulated via a rod 78 to a lever arm on a yoke 60' which is fastened to the underside of table 59 and carries a pair of pneumatic valves 8 and 11; an identical yoke 60, also secured to the underside of the table, sup ports a valve 7 as Well as the shaft 61 of motor switch 64. Two identical mounting plates 36 and 36 are likewise fastened to the lower table surface and serve as supports for a pair of pneumatic cylinders 10 and 28, respectively.

The mounting plates 36 and 36 have the shape illustrated in FIG. 3 in which plate 36 is shown provided with bores 37, 38 and 41 to accommodate various bolts or studs, bosses 39 and 40 serving as bolt guides for similar mounting purposes, and a shaft 42 rotatably journaled therein. A flange 58 serves for the attachment of the plate 36 to the table 59. In the assembly of FIG. 4, in which the bosses 39 and 40 are not utilized, the pneumatic motor or piston cylinder 10 is held in place by jaws 88 secured to the plate 36 by bolts traversing the bores 37. Shaft 42 serves as a fulcrum for a lever 43 with several holes 44, one of these holes being engaged by a universal joint forming a socket 45 for the control rod 46. Another arm 47, also pivoted on shaft 42 and rigid with arm 43, is articulated to the piston 52 of cylinder 10 which has a telescoped extension 48, 49 secured to it by means of interconnected blocks 53, 54, the rod-shaped transmission member 49 being received in a blind axial bore of the tubular transmission member 48. The articulated linkage between piston 52 and rod 46 has been generally designated by the numeral 13.

The companion plate 36 shown in FIG. 8, in which elements corresponding to those of FIGS. 3 and 4 have been distinguished therefrom by primes, carries the pneumatic cylinder 28 whose clamping jaws 88' are secured to it at the bores 38 (FIG. 3). The transmission 13' shown in FIG. 8 is substantially identical with the linkage 13 of FIG. 4. In addition, however, arm 47' is rigid with a cam plate 57 which swings with it about the stud shaft 42' and acts upon a pneumatic valve 21 fastened to the plate 36' by way of the bosses 39' thereof. The cam 57 is adjustable with reference to arm 47 by being provided with an arcuate slot 56 which is traversed by a screw 94.

The yoke 60, shown in FIG. 5, has two arms in which the shaft 61 is journaled, the pneumatic valve 7 being positioned between these arms so as to be actuatable by a cam 62 carried on shaft 61. Fixed to the free end of shaft 61, by means of a pin 67, is a coupling 66 with a notch 68 adapted to mate with an extension shaft forming part of the switch 64 (see also FIG. 2).

Yoke 60, illustrated in FIGS. 6 and 7, is structurally identical with yoke 60 and supports a shaft 61 with a pair of cams 79, 81 mounted thereon. Shaft 61' carries at one end the aforementioned lever arm 70, linked to pedal-controlled rod 78, and is provided on its opposite end with an indexing disk 71 having pins 72, 73 radially projecting therefrom. These pins act as stop members in cooperation with a casing 74, externally secured to one of the arms of the yoke, in which a pin 75 is vertically slidable under pressure of a spring 76. The tip of pin 75, bearing upon the periphery of disk 71, is adapted to drop into a notch 77 on that periphery to hold the disk in an intermediate position in which the lever arm 70 occupies the position I shown in dot-dash lines in FIG. 7. The two extreme positions, respectively defined by the pins 73 and 72, have been shown in solid lines and at II in dot-dash lines. Disk 71 also has a radial bore 83, next to the one accommodating the pin 73, which is not used in the arrangement of FIGS. 6 and 7.

The operation of the servosystem described in conjunction with FIGS. 1-8 will now be described with reference to FIG. 14. This figure diagrammatically shows the pneumatic cylinders 10 and 28, together with their piston linkages 13 and 13 leading to the rods 46 and 46', along with the pneumatic valves 7, 8, 11 and 21 as well as the pedal 68. A source of air, steam or other fluid under pressure has been indicated by a pipe 100.

When the motor 65 (FIGS. 1 and 2) is switched on by means of the handle 63, the cam 62 seen in FIG. opens the valve 7 so that fluid from line 100 passes through this valve and the normally open valves 8 and 21, connected in series therewith in a conduit 101, to the bottom of cylinder to lift its piston 52. This action displaces the rod 46 along with the handle 31 to raise the presser foot 87 (FIG. 1) preparatorily to the deposition of a workpiece on machine base 86. When the workpiece is in place, the operator steps on the pedal 68 to rotate it counterclockwise as viewed in FIG. 14; its initial rotation, communicated via rod 78 to the arm 70 of FIGS. 6 and 7, brings about a displacement into the indexed position I (FIG. 7) in which cam 79 actuates the valve 8 so as to cut off the fluid supply from the cylinder 10 and to vent the latter to the atmosphere. Piston 52, under the pressure of its spring 89, descends to its bottom position (as viewed in FIG. 14) and entrains the male member 49 (FIG. 4) of its two-part extension 48, 49, the female member 48 following it, under the action of a spring (not shown) bearing upon the presser foot 87 of the machine, only to the extent permitted by the thickness of the workpiece. Next, the operator continues the swing of pedal 68 so that, as the assembly shown in FIGS. 6 and 7 reaches the position II, cam 81 opens the valve 11 while cam 79 maintains its effect upon valve 8. Fluid now streams into the cylinder 28 through a conduit 102 and lifts the piston 52 thereof against the force of its spring 89, the linkage 30' displacing the rod 46' to start the operation of machine 80. At the same time, as will be apparent from FIG. 8, transmission 13' by cam 57 closes the valve 21 to disconnect the cylinder 10 from its supply conduit 101, thereby insulating it from the valve 8 and preventing the readmission of fluid into the cylinder upon the subsequent release of pedal 68. The pedal, under the action of its restoring spring 90 (FIG. 1), thereupon returns to normal whereby fluid pressure is removed from cylinder 28 and its piston 52 descends, yet a part of the transmission 13 including member 48 and cam 57 remains in an off-normal position in which it is held by the control rod 46' and the associated starting member until the latter is restored by the program unit, not shown, upon completion of a sewing cycle. Thus, the splitting of each linkage 13, 13' into two separate parts, interconnected only for pressure transmission, has the advantage of relieving the rods 46, 46 and their associated mechanisms from the stress of the restoring spring 52, 52 of the pneumatic pistons.

Another advantage of the split linkage resides in increased adjustability to fit different requirements, as will be apparent from the following description of the modified assembly illustrated in FIGS. 9-11. This assembly comprises a pneumatic cylinder 22, replacing cylinder 10 of the preceding embodiment, which is carried on the mounting plate 36 and has connected to it a linkage 13a differing from the aforedescribed linkages 13 and 13' mainly by the presence of a cam 24 on its piston 52a. Cam 24 has a shoulder 55 to which a block 53a, rigid with the male transmission member 49a, is articulated; the corresponding female member 48a, whose blind bore has been shown at 50, contains a removable spacer 51 designed to adapt the free path of rod-shaped transmission member 49:: to the stroke length of piston 52a in cylinder 52.

A valve 27, secured to the mounting plate 36 by its bosses 40 (FIG. 3), has its stem overlain by a lever 90 articulated to the valve body at 91; the free end of lever 90 has pivoted to it an arm 26 with a roller 25 acting as a follower for cam 24. Arm 26, which can swing limitedly clockwise from its position shown in FIG. 10, is normally maintained in that position by a spring 92. Thus, when the piston 52a is retracted into the cylinder 22, cam 24, moving to the left, depresses the roller 25 and actuates the valve 27; when the piston 52a is driven outwardly, cam 24 in its rightward motion merely deflects the roller 25 and the arm 26 into the position shown in dot-dash lines in FIG. 10 so that the valve 27 is not affected thereby.

The operation of this un-idirectionally effective camming arrangement will be described with reference to FIG. 15 which diagrammatically illustrates a servosystem controlled by a photoelectric scanner 93 instead of the aforedescribed pedal 68. Scanner 93, upon detecting the edge of an approaching fabric or other workpiece, produces a single pulse which is sharpened by a network 18, e.g. a Schmitt trigger circuit, and amplified at 19 efore being applied to a solenoid valve 20. This solenoid valve has been shown supported on the mounting plate 36 in FIG. 9. With pneumatic valve 7 open, as

before, in the running condition of the drive motor 65 (FIGS. 1 and 2), solenoid valve 20 normally admits pressure fluid by way of the likewise open valve 21 to the bottom of cylinder 22 to raise its piston 52a so as to maintain the presser foot 87 of the machine in a released position. When a pulse from the output of scanner 93 appears in the output of amplifier 19, solenoid valve 20 cuts off pressure from cylinder 22 and vents it to the atmosphere, thereby letting the piston 52a descend under the action of its spring 89a, and allows the presser foot to follow suit in the manner previously described. The descent of the piston, furthermore, opens the normally closed pneumatic valve 27 by the action of a camming assembly 23-26 so that fluid now streams into the cylinder 28 to raise its piston 52; the latter, in the manner described in connection with FIG. 14, starts the feeding and sewing mechanism and opens the valve 21 to insulate the cylinder 22 against further fluid pressure. When valve 21 closes thereafter upon the completion of the sewing cycle, fluid from source 100 is again able to enter the cylinder 22 to unclamp the fabric or other workpiece held engaged by the presser foot. It will thus be seen that the system of FIG. 15 is particularly adapted for an arrangement in which the workpieces are automatically delivered to and possibly taken from the machine by suitable conveyor means.

In FIGS. 12 and 13 I have shown a single yoke 60" which replaces the two yokes 60, 60 of the prior embodiments and is of the same construction. Yoke 60 carries the aforedescribed shaft 61' on which, however, a further cam 82 has been disposed alongside the cams 79 and 81. Disk 71, as best seen in FIG. 13, has been modified by the insertion of a plug 85 into the bore previously occupied by pin 73 and the transfer of this pin to bore 83 (FIGS. 6 and 7). Thus, the disk 71 is now free to turn, from the position shown in full lines in FIG. 13, not only counterclockwise into positions I and II previously referred to, but also clockwise into a position III also shown in dot-dash lines. The yoke 60" accommodates between its arms a set of three valves 32, 33 and 34 respectively cooperating with the cams 79, 82 and 81.

Reference is now made to FIG. 16 for a description of a system utilizing the three valves 3234 of FIGS. 12 and 13. The system is designed for use with machines, e.g. for sewing grommets, which operate on relatively heavy workpieces such as coats, jackets or the like requiring proper positioning below the presser foot under the control of the operator. In order that the latter may have both hands free for this work, the pedal 68 is again used in this system. When this pedal is swung partially counterclockwise as viewed in FIG. 16, disk 71 and arm 70 assume the position I in FIG. 13 in which pin 75 drops into notch 77 while the cam 79 opens the normally closed valve 32. Pressure fluid now enters a pneumatic cylinder 30, replacing the cylinder of FIG. 14, whose piston is linked via rod 46 with the clamping lever 31 and which now operates this lever to lower the presser foot upon the fabric. If the latter is not properly positioned, the operator reverses the pedal 68 so that, as a result of its clockwise rotation, disk 71 and arm 70 assume the position III in disk 13 whereby cam 82 opens the normally closed valve 33 and admits fluid into the cylinder 30 in the opposite direction, thereby again lifting the presser foot. The pedal 68 is then once more rotated counterclockwise, to reclamp the workpiece, whereupon the rotation of the pedal is continued in the same sense until position II (FIG. 13) is reached in which cam 81 opens the normally closed valve 34. Pressure fluid now enters a cylinder 35, replacing cylinder 28 of the prior embodiments, to displace the rod 46' for starting the machine. The pedal is then returned only to position I in which the disk 71 is indexed by the pin 75. The neutral position shown in full lines in FIG. 13 is in this case without much practical significance so 6 that, when the operation is completed, the operator may simply leave the assembly in position III for keeping the presser foot raised.

FIG. 17 shows the same valves as FIG. 14, except for valves 8 and 11 which have been replaced by two solenoid valves 14 and 15, respectively. A manual switch 16, upon being depressed by the operator, closes first a pair of contacts 16' and then also a pair of contacts 16" to operate the solenoid valves 14 and 15 in staggered succession. Solenoid valve 14, which had previously admitted fluid from source to cylinder 10 to raise its piston, now vents that cylinder to bring about the aforedescribed clamping operation; valve 15, immediately thereafter, applies pressure to cylinder 28 to initiate the sewing cycle and to operate the pneumatic valve 21 for insulating the cylinder 10 from its pressure source. The switch 16 maythereupon be released and the system operates in the same manner as has been described with reference to FIGS. 14 and 15.

Various modifications of the arrangements described and illustrated are of course possible without departing from the spirit and scope of my invention as defined in the appended claims.

I claim:

1. In a sewing machine having clamping means for' pressing a workpiece against a base and further having start means for initiating a sewing cycle on said workpiece, the combination therewith of a servo system including first pneumatic means coupled with'said clamping means, second pneumatic means coupled with said start means, a single control element coupled with both said pneumatic means for actuating same in staggered relationship, thereby successively operating said clamping means and said start means, said pneumatic means each including a respective piston-and-cylinder arrangement and a respective valve means connected with the respective piston-and-cylinder arrangement for controlling same, said valve means being mechanically connected with said element for actuation thereby, and further valve means operable by said second pneumatic means for blocking operation of the piston-and-cylinder arrangement of said first pneumatic means by the valve means thereof.

2. The combination defined in claim 1 wherein said control element is progressively displaceable from a normal position into a first off-normal position for actuation of said first pneumatic means and into a second off-normal position for actuation of both said pneumatic means.

3. The combination defined in claim 2 wherein said control element is a pedal swingable in one direction into said first and second off-normal positions and in the opposite direction into a further ofi-normal position for deactivating said first pneumatic means, thereby releasing said clamping means.

4. In a sewing machine having clamping means for pressing a workpiece against a base and further having start means for initiating a sewing cycle on said workpiece, the combination therewith of a servo system including first pneumatic means coupled with said clamping means, second pneumatic means coupled with said start means, and a single control element coupled with both said pneumatic means for actuating same in staggered relationship, thereby successively operating said clamping means and said start means; said first pneumatic means comprising a first cylinder, a first piston in said first cylinder linked with said clamping means, first conduit means normally connecting said first cylinder to a source of pressure fluid, and first valve means in said first conduit means actuatable by said element for disconnecting said first cylinder from said source and connecting it instead to atmos:

phere, thereby moving said first piston from an unclamping position into a clamping position; said second pneumatic means comprising a second cylinder, a second piston in said second cylinder linked with said start means, second conduit means leading to said second cylinder and to said source of pressure fluid, normally closed second valve means in said second conduit means openable by said element for connecting said second cylinder to said source, thereby moving said second piston into a machinestarting position, and normally open further valve means closable by said second piston in response to fluid pressure for insulating said first cylinder from said first valve means, thereby maintaining said first piston in its clamping position irrespectively of the position of said element.

5. In a sewing machine having clamping means for pressing a workpiece against a base and further having start means for initiating a sewing cycle on said workpiece, the combination therwith of a servosystem including first pneumatic means coupled with said clamping means, second pneumatic means coupled with said start means, a single control element coupled with both said pneumatic means for actuating same in staggered relationship, thereby successively operating said clamping means and said start means, said first pneumatic means comprising a first cylinder, a first piston in said first cylinder linked with said clamping means, first conduit means normally connecting said first cylinder to a source of pressure fluid, and first valve means in said first conduit means actuatable by said element for disconnecting said first cylinder from said source and connecting it instead to atmosphere, thereby moving said first piston from an unclamping position into a clamping position; said second pneumatic means comprising a second cylinder, a second piston in said second cylinder linked with said start means, second conduit means leading to said second cylinder and to said source of pressure fluid, normally closed second valve means in said second conduit means openable by said element for connecting said second cylinder to said source, thereby moving said second piston into a machine-starting position, and normally open further valve means closable by said second piston in response to fluid pressure for insulating said first cylinder from said first valve means, thereby maintaining said first piston in its clamping position irrespectively of the position of said element, said second valve means being openable by said element through the intermediary of said first valve means and said first cylinder, said first piston being provided with transmission means coupled with said second valve means.

6. The combination defined in claim wherein said transmission means comprises cam means on said first piston and unidirectionally eflective cam-follower means linked with said second valve means.

7. The combination defined in claim 5 wherein said element comprises an automatic detector sensing the approach of the workpiece.

8. In a sewing machine having clamping means for pressing a workpiece against a base and further having start means for initiating a sewing cycle on said workpiece, the combination therewith of a servosystem including first pneumatic means coupled with said clamping means, second pneumatic means coupled with said start means, and a single control element coupled with both said pneumatic means for actuating same in staggered relationship, thereby successively operating said clamping means and said start means; said first pneumatic means comprising a first cylinder, a first piston in said first cylinder linked with said clamping means, first conduit means normally connecting said first cylinder to a source of pressure fluid, and first valve means in said first conduit means actuatable by said element for disconnecting said first cylinder from said source and connecting it instead to atmosphere, thereby moving said first piston from an unclamping position into a clamping position; said second pneumatic means comprising a second cylinder, a second piston in said second cylinder linked with said start means, second conduit means leading to said second cylinder and to said source of pressure fluid, normally closed second valve means in said second conduit means openable by said element for connecting said second cylinder to said source, thereby moving said second piston into a machine-starting position, and normally open further valve means closable by said second piston in response to fluid pressure for insulating said first cylinder from said first valve means, thereby maintaining said first piston in its clamping position, irrespectively of the position of said element, said second piston comprising two telescoped portions including a spring-loaded first portion and a second portion positively connected with said start means, said second portion being coupled with said further valve means for holding same closed until restoration of said start means to an initial position.

9. In a sewing machine provided with a supporting table, clamping means for pressing a workpiece against a base on said table and start means for initiating a sewing cycle on said workpiece, the combination therewith of a servosystem including two mounting plates on the underside of said table, at least one yoke on the underside of said table, a pair of pneumatic cylinders and pistons respectively secured to said plates, valve means for controlling said pistons disposed on said yoke, a shaft spanning said yoke, cam means for actuating said valve means on said shaft, a pair of links respectively connecting said pistons with said clamping means and with said start means, a single control element on said table, means including a source of fluid pressure, said element, said cam means, said valve means and said pistons for successively operating said clamping means and said start means, cam means on the piston linked with said clamping means, and cam-controlled additional valve means on the plate supporting the last-mentioned piston for actuation by the latter, said additional valve means being included in a pneumatic circuit for operating the piston linked with said start means.

1%). In a sewing machine provided with a supporting table, clamping means for pressing a workpiece against a base on said table and start means for initiating a sewing cycle on said workpiece, the combination therewith of a servosystem including two mounting plates on the underside of said table, at least one yoke on the underside of said table, a pair of pneumatic cylinders and pistons respectively secured to said plates, valve means for controlling said pistons disposed on said yoke, a shaft spanning said yoke, cam means for actuating said valve means on said shaft, a pair of links respectively connecting said pistons with said clamping means and with said start means, a single control element on said table, means including a source of fluid pressure, said element, said cam means, said valve means and said pistons for successively operating said clamping means and said start means, and articulated transmission means pivoted on each of said mounting plates and connecting the respective pistons to the associated links, at least one of said transmission means including an arm constituted by a rod-shaped member and a tubular member telescopically receiving said rod-shaped member.

11. The combination defined in claim 10 wherein said tubular member has a blind axial bore accommodating said rod-shaped member, further comprising spacer means removably disposed in said bore for contact with said rodshaped member.

References Cited by the Examiner UNITED STATES PATENTS 2,718,201 9/1955 Kindseth et al 112219 X 2,722,184 11/1955 Sweet 112-219 X 2,750,908 5/1956 Odermann et a1 112235 2,758,556 8/1956 Hopkins 112219 X 2,764,112 9/1956 Happe 112-219 X 3,156,204 11/1964 Harnish et al 1122l9 X FRANK J. COHEN, Primary Examiner.

ROBERT V. SLOAN, Examiner. 

1. IN A SEWING MACHINE HAVING CLAMPING MEANS FOR PRESSING A WORKPIECE AGAINST A BASE AND FURTHER HAVING START MEANS FOR INITIATING A SEWING CYCLE ON SAID WORKPIECE, THE COMBINATION THEREWITH OF A SERVO SYSTEM INCLUDING FIRST PNEUMATIC MEANS COUPLED WITH SAID CLAMPING MEANS, SECOND PNEUMATIC MEANS COUPED WITH SAID START MEANS, A SINGLE CONTROL ELEMENT COUPLED WITH BOTH SAID PNEUMATIC MEANS FOR ACTUATING SAME IN STAGGERED RELATIONSHIP, THEREBY SUCCESSIVELY OPERATING SAID CLAMPING MEANS AND SAID START MEANS, SAID PNEUMATIC MEANS EACH INCLUDING A RESPECTIVE PISTON-AND-CYLINDER ARRANGEMENT AND A RESPECTIVE VALVE MEANS CONNECTED WITH THE RESPECTIVE PISTON-AND-CYLINDER ARRANGEMENT FOR CONTROLLING SAME, SAID VALVE MEANS BEING MECHANICALLY CONNECTED WITH SAID ELEMENT FOR ACTUATING THEREBY, AND FURTHER VALVE MEANS OPERABLE BY SAID SECOND PNEUMATIC MEANS FOR BLOCKING OPERATION OF THE PISTON-AND-CYLINDER ARRANGEMENT OF SAID FIRST PNEUMATIC MEANS BY THE VALVE MEANS THEREOF. 